All the heart

בכל לבבך בשני יצריך ביצר טוב וביצר הרע
.ברכות נד

How do we serve Hashem with our evil inclination?
The simple explanation is that through overcoming the evil inclination we serve Hashem. But even if we stumbled and transgressed we could utilize our listening to the evil inclination in the service of Hashem by doing Teshuva.